35 research outputs found

    Variants of the human RAD52 gene confer defects in ionizing radiation resistance and homologous recombination repair in budding yeast

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    RAD52 is a structurally and functionally conserved component of the DNA double-strand break (DSB) repair apparatus from budding yeast to humans. We recently showed that expressing the human gene, HsRAD52 in rad52 mutant budding yeast cells can suppress both their ionizing radiation (IR) sensitivity and homologous recombination repair (HRR) defects. Intriguingly, we observed that HsRAD52 supports DSB repair by a mechanism of HRR that conserves genome structure and is independent of the canonical HR machinery. In this study we report that naturally occurring variants of HsRAD52, one of which suppresses the pathogenicity of BRCA2 mutations, were unable to suppress the IR sensitivity and HRR defects of rad52 mutant yeast cells, but fully suppressed a defect in DSB repair by single-strand annealing (SSA). This failure to suppress both IR sensitivity and the HRR defect correlated with an inability of HsRAD52 protein to associate with and drive an interaction between genomic sequences during DSB repair by HRR. These results suggest that HsRAD52 supports multiple, distinct DSB repair apparatuses in budding yeast cells and help further define its mechanism of action in HRR. They also imply that disruption of HsRAD52-dependent HRR in BRCA2-defective human cells may contribute to protection against tumorigenesis and provide a target for killing BRCA2-defective cancers

    Establishment and Validation of Computational Model for MT1-MMP Dependent ECM Degradation and Intervention Strategies

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    MT1-MMP is a potent invasion-promoting membrane protease employed by aggressive cancer cells. MT1-MMP localizes preferentially at membrane protrusions called invadopodia where it plays a central role in degradation of the surrounding extracellular matrix (ECM). Previous reports suggested a role for a continuous supply of MT1-MMP in ECM degradation. However, the turnover rate of MT1-MMP and the extent to which the turnover contributes to the ECM degradation at invadopodia have not been clarified. To approach this problem, we first performed FRAP (Fluorescence Recovery after Photobleaching) experiments with fluorescence-tagged MT1-MMP focusing on a single invadopodium and found very rapid recovery in FRAP signals, approximated by double-exponential plots with time constants of 26 s and 259 s. The recovery depended primarily on vesicle transport, but negligibly on lateral diffusion. Next we constructed a computational model employing the observed kinetics of the FRAP experiments. The simulations successfully reproduced our FRAP experiments. Next we inhibited the vesicle transport both experimentally, and in simulation. Addition of drugs inhibiting vesicle transport blocked ECM degradation experimentally, and the simulation showed no appreciable ECM degradation under conditions inhibiting vesicle transport. In addition, the degree of the reduction in ECM degradation depended on the degree of the reduction in the MT1-MMP turnover. Thus, our experiments and simulations have established the role of the rapid turnover of MT1-MMP in ECM degradation at invadopodia. Furthermore, our simulations suggested synergetic contributions of proteolytic activity and the MT1-MMP turnover to ECM degradation because there was a nonlinear and marked reduction in ECM degradation if both factors were reduced simultaneously. Thus our computational model provides a new in silico tool to design and evaluate intervention strategies in cancer cell invasion

    Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

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    BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

    Human and murine clonal CD8+ T cell expansions arise during tuberculosis because of TCR selection

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    The immune system can recognize virtually any antigen, yet T cell responses against several pathogens, including Mycobacterium tuberculosis, are restricted to a limited number of immunodominant epitopes. The host factors that affect immunodominance are incompletely understood. Whether immunodominant epitopes elicit protective CD8+ T cell responses or instead act as decoys to subvert immunity and allow pathogens to establish chronic infection is unknown. Here we show that anatomically distinct human granulomas contain clonally expanded CD8+ T cells with overlapping T cell receptor (TCR) repertoires. Similarly, the murine CD8+ T cell response against M. tuberculosis is dominated by TB10.44-11-specific T cells with extreme TCRß bias. Using a retro genic model of TB10.44-11-specific CD8+ Tcells, we show that TCR dominance can arise because of competition between clonotypes driven by differences in affinity. Finally, we demonstrate that TB10.4-specific CD8+ T cells mediate protection against tuberculosis, which requires interferon-? production and TAP1-dependent antigen presentation in vivo. Our study of how immunodominance, biased TCR repertoires, and protection are inter-related, provides a new way to measure the quality of T cell immunity, which if applied to vaccine evaluation, could enhance our understanding of how to elicit protective T cell immunity.This work was supported by the Portuguese Foundation for Science and Technology individual fellowship (CNA) www.fct.pt, a National Institutes of Health Grant R01 AI106725 (SMB) www.nih.gov, and a Center for AIDS Research Grant P30 AI 060354 (SMB) www.nih.gov. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

    Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

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    Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

    Preoperative heart rate variability and postoperative delirium in the elderly

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    Einleitung Eine Imbalance des Parasympathikus wird als Auslöser eines postoperativen Delirs diskutiert. Die Etablierung einer validen Risikostratifizierung vor Operationen ist für Menschen im höheren Lebensalter notwendig, um das individuelle postoperative Delir (POD) Risiko reduzieren zu können. Soweit wir wissen, existieren keine prospektiven präoperativen HRV Untersuchungen an operierten Älteren und dem Auftreten eines POD. Es liegen keine Daten vor, die einen Vergleich zulassen. Ziel dieser Studie war, ob präoperative Unterschiede der Parasympathikus Aktivität bei Patienten*innen mit und ohne POD durch HRV Messungen detektiert werden können. Methodik Diese Untersuchung wurde bei 174 Patienten*innen der BioCog-Studie ("Biomarker Development for Postoperative Cognitive Impairment in the Elderly") durchgeführt, die mindestens 65 Jahre alt waren. Beobachtet wurde an einem gemischt chirurgischen Kollektiv die präoperative HRV und das Auftreten eines POD nach Kriterien der BioCog-Studie. Die HRV wurde anhand der Frequenzbereichs Methode [die die Parameter Low-Frequency Power (LF) und High-Frequency Power (HF) und High-Frequency Power bezogen auf Normalized Units (HFnu) sowie die LF/HF Ratio umfasst] gemessen. HF und HFnu erlauben Aussagen über die parasympathische Aktivität, die LF/HF Ratio über die sympathovagale Balance. Weiterführend wurden die Patienten*innen mit besonders hoher und niedriger Parasympathikus Aktivität (anhand der LF/HF Ratio) analysiert. Ergebnisse Im Median waren die 174 Patienten*innen 72 Jahre alt, 46 % (n=80) waren weiblich. Ein POD erlitten 21 % (n=37) der Patienten*innen. Signifikante Gruppenunterschiede in den HRV Parametern zwischen Patienten*innen mit und ohne POD zeigten sich nicht. Logistische Regressionsanalysen für jeden HRV Parameter zeigten keine Assoziation zu POD (HRV Parameter, Odds Ratio (95%-Konfidenz Intervall) p-Wert; Total Power 1,00 (1,00 bis 1,00), p-Wert: 0,144; Low-Frequency Power 1,00 (1,00 bis 1,00), p-Wert: 0,730; High-Frequency Power 1,00 (1,00 bis 1,00), p-Wert: 0,818; LF/HF Ratio 0,99 (0,88 bis 1,12), p-Wert: 0,952; HF(nu) 0,997 (0,966 bis 1,030) , p-Wert: 0,870). Besonders hohe Parasympathikus Aktivität (LF/HF ≤ 0,4) steigert die POD Wahrscheinlichkeit um ca. 6 % (OR: 6,408; [KI95%: 1,125 - 36,517]; p-Wert: 0,036). Schlussfolgerung Es ist anzunehmen, dass Patienten*innen, deren Vegetativum vor Operationen überdurchschnittlich aktiviert ist, weiteren Anforderungen mit einer nur eingeschränkten physiologischen Reflexantwort begegnen können. Extremwertanalysen der LF/HF Ratio zeigten, dass eine Reduktion der LF/HF Ratio, sprich eine besonders hohe Parasympathikus Aktivität, mit einem erhöhten POD Risiko verbunden ist. Fehlende Referenzwerte, hohe interindividuelle HRV Varianz und ein methodenbedingter Selektionsbias stellt die HRV Frequenzbereichs Methode im klinischen Alltag vor Limitationen.Backround An imbalance of the parasympathetic nervous system is discussed as the trigger of a postoperative delirium (POD). Establishing a valid risk stratification before surgery is necessary for older people to reduce the individual POD risk. To the best of our knowledge there are no prospective preoperative heart rate variability (HRV) examinations on operated elderly people and the appearance of a POD. The aim of this study was to determine whether preoperative differences in parasympathetic activity in patients with and without POD could be detected by HRV measurements. Methods The BioCog-Study ("Biomarkers Development for Postoperative Cognitive Impairment in the Elderly") was designed to the development of a biomarker panel to assess the individual POD risk. This analysis is based on a subgroup of the observational multicenter BioCog-Study comprising patients, who were at least 65 years of age. In a mixed surgical cohort, the preoperative HRV and POD according to criteria of the BioCog-Study were observed. HRV was measured by the Frequency Domain Method [which includes the parameters Low-Frequency Power (LF), High-Frequency Power (HF), High-Frequency Power related to Normalized Units (HFnu) and the LF/HF Ratio]. HF and HF(nu) evaluate the parasympathetic activity, the LF/HF Ratio the sympathovagal balance. The patients with particularly high and low parasympathetic activity were further analyzed (using the LF/HF Ratio). Results The analysis included 174 patients, of whom 45.9% (n=80) were female, median age was 72 years. POD suffered 21.3% (n=37) of the patients. No significant group differences in the HRV Parameters were detected. Logistic regression analyzes for each HRV Parameter showed no POD association (HRV parameter, odds ratio (95% confidence interval) p-value; Total Power 1.00 (1.00 to 1.00), p-value: 0.144; Low- Frequency Power 1.00 (1.00 to 1.00), p-value: 0.730; High-Frequency Power 1.00 (1.00 to 1.00), p-value: 0.818; LF / HF Ratio 0.99 (0.88 to 1.12), p-value: 0.952; HF(nu) 0.997 (0.966 to 1.030), p-value: 0.870). Particularly high parasympathetic activity (LF/HF ≤ 0.4) increases the POD risk by approx. 6% (OR: 6.408; [KI95%: 1.125 - 36.517]; p: 0.036). Conclusion It can be assumed that patients with preoperatively pitched vegetative state are limited in physiological reflex response for further requirements. Extreme value analyzes of the LF/HF Ratio showed that a reduction, i.e. a particularly high parasympathetic activity, is associated with an increased POD risk. Missing reference values, high interindividual HRV variance and a method-related selection bias pose limitation to the use of HRV frequency method in everyday clinical practice
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